As a wireless network to be formed in a human body, a network called a body area network is known. For the body area network, for example a hub as a center device and a node as a terminal device are mounted on a human body and communication is performed between the hub and the node. A terminal includes a biosensor, and wirelessly transmits information or the like acquired in the biosensor to the center device. Depending on the information to be wirelessly transmitted, there is the one that needs to be preferentially and surely transmitted as emergency data. In IEEE802.15.6 which is a standard specification relating to the body area network, a mechanism of allocating time exclusive for the emergency data immediately after a transmission timing of a beacon signal is used as a measure for the time of emergency data generation.
Also, though not the body area network, a mechanism of securing transmission time of the emergency data by having the node transmit an emergency communication request when the emergency data is generated is considered. The emergency communication request is sent by a control channel of a high priority degree for the emergency data. In this method, an access point which receives the emergency communication request notifies all the terminals that there is emergency data transmission at the next downlink timing. Thereafter, the node where the emergency data is generated occupies the control channel and a data channel and transmits the emergency data, and the other nodes stop transmission and reception during the period.
Also, as a different method, a mechanism of transmitting the same data again by the other data channel in the case of important data is also considered. The other data channel is used only when transmitting backup data when the important data is generated, and the backup data of the important data is transmitted at a predetermined timing.
By a conventional scheme of IEE802.15.6, it is needed to allocate the time for the emergency data transmission beforehand, and the allocated time is wasted in a normal operation in which the emergency data is not generated. Also, in the above-described method using the control channel of the high priority degree, while a scheme using the plurality of control channel and data channels is a prerequisite, when the emergency data is generated, it is needed to make the other nodes perform an operation different from a normal operation. Further, in the method of retransmitting the important data by the other data channel, it is needed to secure the data channel for the backup transmission.